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| Credit WHO |
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Over the past hour it has emerged the the UK is investigating the detection of multiple poliovirus positive samples from local sewage surveillance, which is suggestive of potential limited community spread of a vaccine-derived poliovirus (VDPV).
While concerning, most inhabitants of London are fully protected by the polio vaccine, but it is possible that some people who were never fully vaccinated, are still susceptible to the virus.
Although most western countries stopped using the oral polio vaccine (OPV) in favor of the inactivated polio vaccine (IPV) decades ago - and most of the world followed suit a few years ago (see Polio Vaccines: The Big Switch Begins) - a few countries still use the oral vaccines to combat outbreaks.
The oral (Sabin) polio vaccine (OPV) contains three attenuated (weakened) polio virus strains that activate an immune response in the body, and for a few weeks causes the weakened virus to be shed in the feces.
This is considered a `good’ side effect, for in areas with poor sanitation, this vaccine-virus can spread in the community for a limited time conveying extra immunity.
But, as the WHO explains, every once in awhile this can go awry.
On rare occasions, if a population is seriously under-immunized, an excreted vaccine-virus can continue to circulate for an extended period of time. The longer it is allowed to survive, the more genetic changes it undergoes. In very rare instances, the vaccine-virus can genetically change into a form that can paralyse – this is what is known as a circulating vaccine-derived poliovirus (cVDPV).First, the press release from the UKHSA, followed by a link and some excerpts from London's response plan.
Poliovirus detected in sewage from North and East London
Investigation underway to protect public, who are urged to ensure polio vaccines are up to date, especially parents of young children who may have missed an immunisation opportunity.
From:UK Health Security Agency Published 22 June 2022
The UK Heath Security Agency (UKHSA), working with the Medicines and Healthcare products Regulatory Agency (MHRA), has found poliovirus in sewage samples collected from the London Beckton Sewage Treatment Works.
As part of routine surveillance, it is normal for 1 to 3 ‘vaccine-like’ polioviruses to be detected each year in UK sewage samples but these have always been one-off findings that were not detected again. These previous detections occurred when an individual vaccinated overseas with the live oral polio vaccine (OPV) returned or travelled to the UK and briefly ‘shed’ traces of the vaccine-like poliovirus in their faeces.
Investigations are underway after several closely-related viruses were found in sewage samples taken between February and May. The virus has continued to evolve and is now classified as a ‘vaccine-derived’ poliovirus type 2 (VDPV2), which on rare occasions can cause serious illness, such as paralysis, in people who are not fully vaccinated.
The detection of a VDPV2 suggests it is likely there has been some spread between closely-linked individuals in North and East London and that they are now shedding the type 2 poliovirus strain in their faeces. The virus has only been detected in sewage samples and no associated cases of paralysis have been reported – but investigations will aim to establish if any community transmission is occurring.
The last case of wild polio contracted in the UK was confirmed in 1984. The UK was declared polio-free in 2003.
Dr Vanessa Saliba, Consultant Epidemiologist at UKHSA said:
Vaccine-derived poliovirus is rare and the risk to the public overall is extremely low.
Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower. On rare occasions it can cause paralysis in people who are not fully vaccinated so if you or your child are not up to date with your polio vaccinations it’s important you contact your GP to catch up or if unsure check your Red Book. Most of the UK population will be protected from vaccination in childhood, but in some communities with low vaccine coverage, individuals may remain at risk.
We are urgently investigating to better understand the extent of this transmission and the NHS has been asked to swiftly report any suspected cases to the UKHSA, though no cases have been reported or confirmed so far.
Jane Clegg, Chief nurse for the NHS in London said:
The majority of Londoners are fully protected against Polio and won’t need to take any further action, but the NHS will begin reaching out to parents of children aged under 5 in London who are not up to date with their Polio vaccinations to invite them to get protected.
Meanwhile, parents can also check their child’s vaccination status in their Red Book and people should contact their GP surgery to book a vaccination, should they or their child not be fully up to date.
The UK is considered by the World Health Organization to be polio-free, with low-risk for polio transmission due to the high level of vaccine coverage across the population. However, vaccine coverage for childhood vaccines has decreased nationally and especially in parts of London over the past few years, so UKHSA is urging people to check they are up to date with their vaccines.
Wastewater surveillance is being expanded to assess the extent of transmission and identify local areas for targeted action. Healthcare professionals have been alerted to these findings so they can promptly investigate and report anyone presenting with symptoms that could be polio, such as paralysis.
UK Health Security Agency press office
Nobel House
17 Smith Square
London
SW1P 3JR
Emailphe-pressoffice@phe.gov.uk
Telephone020 7654 8400
Out of hours020 8200 4400
A link to the UK's immediate response plan follows:
Guidance
Published 22 June 2022
(Excerpt)
Background and interpretation
The WHO Global Specialised Polio Laboratory located at the National Institute for Biological Standards and Control (NIBSC) conducts routine environmental surveillance for wild type and vaccine-like polio viruses as part of the UK’s commitment to the WHO global polio eradication programme.
Vaccine-like type 2 poliovirus (PV2) isolates have been found in multiple sewage samples collected from the London Beckton Sewage Treatment Works between February and June 2022. This sewage treatment plant covers a large catchment area across North and East London and a population close to 4 million.
During this period, there has been some virus evolution. The virus isolated in the most recent samples contained 6 and 7 VP1 nucleotide changes from the Sabin 2 vaccine strain respectively and therefore is now classified as a vaccine-derived poliovirus (VDPV2).
An average of 1 to 3 poliovirus isolates per year have been detected from UK sewage samples in recent years. However, these have all been single detections which are unrelated to each other. In this instance, the isolates identified between February and June 2022 are genetically related. This has prompted the need to investigate the extent of transmission of this virus in Northeast London.
The most likely scenario is that a recently vaccinated individual entered the UK before February 2022 from a country where oral polio vaccine (OPV) has been used for supplementary immunisation campaigns. While the UK stopped using OPV in 2004, several countries, including Pakistan, Afghanistan and Nigeria have continued to use OPV containing type 2 virus for outbreak control.
UKHSA National Polio Guidelines outline public health actions for consideration when one or more vaccine-related poliovirus type 2 [Level 2 (C)] are detected in environmental samples. A national standard incident has been declared by UKHSA and an Incident Management Team established.
The environmental surveillance is being enhanced in an attempt to assess the extent of VDPV2 transmission and identify areas for targeted action.
